Mycobacterium tuberculosis subverts negative regulatory pathways in human macrophages to drive immunopathology.

Tuberculosis remains a global pandemic and drives lung matrix destruction to transmit. Whilst pathways driving inflammatory responses in macrophages have been relatively well described, negative regulatory pathways are less well defined. We hypothesised that Mycobacterium tuberculosis (Mtb) specifically targets negative regulatory pathways to augment immunopathology. Inhibition of signalling through the PI3K/AKT/mTORC1 pathway increased matrix metalloproteinase-1 (MMP-1) gene expression and secretion, a collagenase central to TB pathogenesis, and multiple pro-inflammatory cytokines. In patients with confirmed pulmonary TB, PI3Kδ expression was absent within granulomas. Furthermore, Mtb infection suppressed PI3Kδ gene expression in macrophages. Interestingly, inhibition of the MNK pathway, downstream of pro-inflammatory p38 and ERK MAPKs, also increased MMP-1 secretion, whilst suppressing secretion of TH1 cytokines. Cross-talk between the PI3K and MNK pathways was demonstrated at the level of eIF4E phosphorylation. Mtb globally suppressed the MMP-inhibitory pathways in macrophages, reducing levels of mRNAs encoding PI3Kδ, mTORC-1 and MNK-1 via upregulation of miRNAs. Therefore, Mtb disrupts negative regulatory pathways at multiple levels in macrophages to drive a tissue-destructive phenotype that facilitates transmission

Comprehensive plasma proteomic profiling reveals biomarkers for active tuberculosis

BACKGROUND. Tuberculosis (TB) kills more people than any other infection, and new diagnostic tests to identify active cases are required. We aimed to discover and verify novel markers for TB in nondepleted plasma. / METHODS. We applied an optimized quantitative proteomics discovery methodology based on multidimensional and orthogonal liquid chromatographic separation combined with high-resolution mass spectrometry to study nondepleted plasma of 11 patients with active TB compared with 10 healthy controls. Prioritized candidates were verified in independent UK (n = 118) and South African cohorts (n = 203). / RESULTS. We generated the most comprehensive TB plasma proteome to date, profiling 5022 proteins spanning 11 orders-of-magnitude concentration range with diverse biochemical and molecular properties. We analyzed the predominantly low–molecular weight subproteome, identifying 46 proteins with significantly increased and 90 with decreased abundance (peptide FDR ≤ 1%, q ≤ 0.05). Verification was performed for novel candidate biomarkers (CFHR5, ILF2) in 2 independent cohorts. Receiver operating characteristics analyses using a 5-protein panel (CFHR5, LRG1, CRP, LBP, and SAA1) exhibited discriminatory power in distinguishing TB from other respiratory diseases (AUC = 0.81). / CONCLUSION. We report the most comprehensive TB plasma proteome to date, identifying novel markers with verification in 2 independent cohorts, leading to a 5-protein biosignature with potential to improve TB diagnosis. With further development, these biomarkers have potential as a diagnostic triage test. / FUNDING. Colciencias, Medical Research Council, Innovate UK, NIHR, Academy of Medical Sciences, Program for Advanced Research Capacities for AIDS, Wellcome Centre for Infectious Diseases Research

The extracellular matrix regulates granuloma necrosis in tuberculosis

A central tenet of tuberculosis pathogenesis is that caseous necrosis leads to extracellular matrix destruction and bacterial transmission. We reconsider the underlying mechanism of tuberculosis pathology and demonstrate that collagen destruction may be a critical initial event, causing caseous necrosis as opposed to resulting from it. In human tuberculosis granulomas, regions of extracellular matrix destruction map to areas of caseous necrosis. In mice, transgenic expression of human matrix metalloproteinase 1 causes caseous necrosis, the pathological hallmark of human tuberculosis. Collagen destruction is the principal pathological difference between humanised mice and wild-type mice with tuberculosis, whereas the release of proinflammatory cytokines does not differ, demonstrating that collagen breakdown may lead to cell death and caseation. To investigate this hypothesis, we developed a 3-dimensional cell culture model of tuberculosis granuloma formation, using bioelectrospray technology. Collagen improved survival of Mycobacterium tuberculosis–infected cells analyzed on the basis of a lactate dehydrogenase release assay, propidium iodide staining, and measurement of the total number of viable cells. Taken together, these findings suggest that collagen destruction is an initial event in tuberculosis immunopathology, leading to caseous necrosis and compromising the immune response, revealing a previously unappreciated role for the extracellular matrix in regulating the host-pathogen interaction

Comprehensive plasma proteomic profiling reveals novel biomarkers for active tuberculosis

Background Tuberculosis (TB) kills more people than any other infection and new diagnostic tests to identify active cases are urgently required. We aimed to discover and verify novel markers for TB in non depleted plasma. Methods We applied an optimised quantitative proteomics discovery methodology based on multidimensional and orthogonal liquid chromatographic separation hyphenated with high-resolution mass spectrometry (q3D LC-MS) to study non-depleted plasma of 11 patients with active TB compared to 10 healthy control donors. Prioritised candidates were verified in an independent UK-based (n=118) and a South African cohorts (n=203). Results We generated the most comprehensive TB plasma proteome to date, profiling 5022 proteins spanning 11 orders-of-magnitude concentration range with diverse biochemical and molecular properties. We further analysed the predominantly low molecular weight sub-proteome; identifying 46 proteins with significantly increased and 90 with decreased abundance (peptide false discovery rate, FDR ≤1%, q77 value ≤0.05). Biological network analysis showed regulation of new pathways involving lipid and organophosphate ester transport. Verification was performed for novel candidate biomarkers (CFHR5, ILF2) in two independent cohorts. These proteins were elevated in both TB and other respiratory diseases (ORD). Receiver-operating-characteristics analyses using a 5-protein panel (CFHR5, LRG1, CRP, LBP and SAA1) exhibited discriminatory power in distinguishing between TB and ORD (AUC =0.81). Conclusions We report the most comprehensive TB plasma proteome to date, identifying numerous novel markers with verification in two independent cohorts, which led to a 5-protein biosignature with potential to improve TB diagnosis. With further development, these biomarkers have potential as a diagnostic triage test

Anti-PD-1 immunotherapy leads to tuberculosis reactivation via dysregulation of TNF-alpha

Previously, we developed a 3-dimensional cell culture model of human tuberculosis (TB) and demonstrated its potential to interrogate the host-pathogen interaction (Tezera et al., 2017a). Here, we use the model to investigate mechanisms whereby immune checkpoint therapy for cancer paradoxically activates TB infection. In patients, PD-1 is expressed in Mycobacterium tuberculosis (Mtb)-infected lung tissue but is absent in areas of immunopathology. In the microsphere model, PD-1 ligands are up-regulated by infection, and the PD-1/PD-L1 axis is further induced by hypoxia. Inhibition of PD-1 signalling increases Mtb growth, and augments cytokine secretion. TNF-α is responsible for accelerated Mtb growth, and TNF-α neutralisation reverses augmented Mtb growth caused by anti-PD-1 treatment. In human TB, pulmonary TNF-α immunoreactivity is increased and circulating PD-1 expression negatively correlates with sputum TNF-α concentrations. Together, our findings demonstrate that PD-1 regulates the immune response in TB, and inhibition of PD-1 accelerates Mtb growth via excessive TNF-α secretion